Cross-posted from the Arnold Support Corner.

Here’s how to install third-party, SPDL-based shaders, like alShaders, so that you can use them with SItoA.

In these instructions, $AL_SHADERS is the location where you extracted the alShaders download. For example, C:\solidangle\alShaders\alShaders-win-0.4.0b18-ai4.2.0.6.

$SITOA_WORKGROUP is the SItoA workgroup location. For example, C:\Users\StephenBlair\softimage\workgroups\sita-3.3.0-2014.

1. Copy the alShader DLLs from
   $AL_SHADERS\bin
   to
   $SITOA_WORKGROUP\Addons\SItoA\Application\Plugins\bin\nt-x86-64

2. Create a spdl folder in your Addons\SItoA\Application folder:
   $SITOA_WORKGROUP\Addons\SItoA\Application\spdl

3. Copy the alShader spdl files from
   $AL_SHADERS\spdl
   to
   $SITOA_WORKGROUP\Addons\SItoA\Application\spdl

4. Restart Softimage. The alShaders should show up in the Render Tree preset manager, and assuming that your version of alShaders is compatible with your SItoA, they’ll work in a render too.
   

Tip Don’t create an alShader from the Arnold > DLL Shaders menu; it won’t pick up the SPDL and you’ll get a raw PPG (and a raw render tree node too).